Brazilian health authority Anvisa said that a volunteer in AstraZeneca's experimental test of a COVID vaccine had died.

AstraZeneca is developing the vaccine with the University of Oxford. In a statement, AstraZeneca said it would continue with the trial.

Oxford confirmed the proposal to continue the trial, saying that after thorough evaluation "there have been no concerns regarding safety of the clinical test."

It was not immediately confirmed whether the volunteer was administered with the COVID vaccine or a placebo as part of the clinical test, and Anvisa disclosed no further details were being released for privacy reasons.

But, according to a Bloomberg report citing a source with knowledge of the matter, the participant had not been given the vaccine.

Shares of AstraZeneca dropped 0.5% following the news.

AstraZeneca said it can't issue any comment on individual cases due to confidentiality and policies on clinical trials and Oxford said it has no concerns with regard safety of the vaccine trial after an independent and careful review

Another source said the trial would have been halted if the volunteer who died had been injected with the vaccine, which would indicate the person was under a control group that was authorized to use a meningitis vaccine.

In a statement, the D'Or Institute, which is overseeing the trial in Rio, said 8,000 volunteers had been given either the COVID vaccine or a placebo. The institute added the comprehensive examination of data gathered up to now "did not raise any doubts regarding the safety of the study," and thus recommended to continue.

AstraZeneca said all medical procedures have been strictly evaluated by health inspectors, including an independent safety monitoring body and regulatory authorities.

The United Kingdom-based biotech group's vaccine trial is temporarily suspended in the U.S. after a patient in Britain reportedly developed symptoms similar with transverse myelitis, or an inflammation of the spinal cord.